There are only two jobs in the Imperium more difficult on a day to day basis than that of a Commissar. That of an Inquisitor, and that of a Space Marine Chapter master. Arguably being a Lord-General as well, but they don't have to make the same kind of judgment calls about the fates of people that we do.
[ Gaunt shrugs his shoulders. ] . But... while the job is hard, it has to be done. I'm not complaining about it, I just try to do the best I can by the men of my regiment, and fight in the service of the Throne.
And there are compensations, as well. I know I'm protecting the future of Humanity as I fight, that's more or less what gets me through.